Fractionation of siderophiles in cosmic spherules and its implications

Fractionation of siderophiles between metal and silicate phases at different oxygen fugacities was extensively studied. Such data could be applied to study the fractionation during formation of stony or iron spherules. However another kind of fractionation exists which takes place within the spherules as they are molten and oxidized in the Earth's atmosphere. During this process two phases develop, one oxidized, the other not. Unoxidized phase is the globule described by shape and high Fe and Ni contents. The process of atmospheric melting is dependent on many factors, one of which is the density of the atmosphere. The density profile of the atmosphere is assumed to have remained constant with time, whereas composition has not. Quantitative explanations of depletions or absence of siderophiles in spherules were initiated.